1. Field of the Invention
The present invention relates to PSGR, a novel prostate specific gene with homology to a G-protein coupled receptor overexpressed in prostate cancer. More specifically, the invention relates to PSGR polynucleotides and the polypeptides encoded by these polynucleotides, and the use of PSGR polynucleotides and polypeptides for detecting disorders of the reproductive system, including disorders of the prostate, particularly the presence of cancer. This invention relates to PSGR polynucleotides and polypeptides as well as vectors, host cells, antibodies directed to PSGR polynucleotides and polypeptides and recombinant and synthetic methods for producing the same. Also provided are diagnostic methods for diagnosing and treating, preventing and/or prognosing disorders related to the prostate, including cancer, and therapeutic methods for treating such disorders. The invention further relates to screening methods for identifying agonists and antagonists of PSGR polynucleotides and polypeptides of the invention. The present invention further relates to methods and/or compositions for inhibiting or enhancing the production and/or function of the PSGR polypeptides of the present invention.
2. Related Art
Prostate cancer is the most common form of cancer among males, with an estimated incidence of 30% in men over the age of 50. Overwhelming clinical evidence shows that human prostate cancer has the propensity to metastasize to bone, and the disease appears to progress inevitably from androgen dependent to androgen refractory status, leading to increased patient mortality. This prevalent disease is currently the second leading cause of cancer death among men in the U.S.
In spite of considerable research into therapies for the disease, prostate cancer remains difficult to treat. Commonly, treatment is based on surgery and/or radiation therapy, but these methods are ineffective in a significant percentage of cases. Two previously identified prostate specific proteinsxe2x80x94prostate specific antigen (PSA) and prostatic acid phosphatase (PAP)xe2x80x94have limited therapeutic and diagnostic potential. For example, PSA levels do not always correlate well with the presence of prostate cancer, being positive in a percentage of non-prostate cancer cases, including benign prostatic hyperplasia (BPH). Furthermore, PSA measurements correlate with prostate volume, and do not indicate the level of metastasis.
In spite of considerable research into therapies for these and other cancers, prostate cancer remains difficult to diagnose and treat effectively. Accordingly, there is a need in the art for improved methods for detecting and treating such cancers.
G-protein coupled receptors (GPCRs ) constitute a major class of proteins responsible for transducing a signal within a cell. GPCRs have three structural domains: an amino terminal extracellular domain; a transmembrane domain containing seven transmembrane segments, three extracellular loops, and three intracellular loops; and a carboxy terminal intracellular domain. Upon binding of a ligand to an extracellular portion of a GPCR, a signal is transduced within the cell that results in a change in a biological or physiological property of the cell. GPCRs, along with G-proteins and effectors (intracellular enzymes and channels modulated by G-proteins), are the components of a modular signalling system that connects the state of intracellular second messangers to extracellular inputs.
GPCRs are a major target for drug action and development. Accordingly, it is valuable to the field of pharmaceutical development to identify and characterize previously unknown GPCRs. The present invention advances the state of the art by providing a previously unidentified prostate specific seven transmembrane GPCR.
The present invention provides isolated nucleic acid molecules comprising, or alternatively, consisting of, a polynucleotide encoding at least a portion of PSGR. Thus, the present invention provides isolated nucleic acid molecules comprising, or alternatively, consisting of, a polynucleotide encoding PSGR having the amino acid sequence shown in FIGS. 1A-B (SEQ ID NO:2); or the amino acid sequence encoded by the cDNA clone (HPRAJ70) deposited as American Type Culture Collection (xe2x80x9cATCCxe2x80x9d) Deposit No. 97131 on Apr. 18, 1995. The ATCC is located at 10801 University Boulevard, Manassas, Va. 20110-2209.
The present invention further provides isolated nucleic acid molecules comprising, or alternatively consisting of, a polynucleotide encoding PSGR having the amino acid sequence shown in FIGS. 2A-B (SEQ ID NO:4).
The present invention also relates to recombinant vectors, which include the isolated nucleic acid molecules of the present invention, and to host cells containing the recombinant vectors, as well as to methods of making such vectors and host cells and for using them for production of PSGR polypeptides or peptides by recombinant techniques.
The invention further provides an isolated PSGR polypeptide having an amino acid sequence encoded by a polynucleotide described herein.
The present invention also provides diagnostic assays such as quantitative and diagnostic assays for detecting levels of PSGR protein. Thus, for instance, a diagnostic assay in accordance with the invention for detecting over-expression of PSGR, or soluble form thereof, compared to normal control tissue samples may be used to detect the presence of tumors.
GPCR genes and gene products are potential causative agents of disease (Spiegel et al., J. Clin. Invest. 92:1119-1125 (1993); McKusick et al., J. Med. Genet. 30:1-26 (1993)). Specific defects in the rhodopsin gene and the V2 vasopressin receptor gene have been shown to cause various forms of retinitis pigmentosum (Nathans et al., Ann. Rev. Genet. 26:403-424 (1992)), nephrogenic diabetes insipidus (Holtzman et al., Hum. Mol. Genet. 2:1201-1204 (1993)). These receptors are of critical importance to both the central nervous system and peripheral physiological processes. Evolutionary analyses suggests that the ancestor of these proteins originally developed in concert with complex body plans and nervous systems.
Thus, the invention further provides cells which express the PSGR polypeptide with a candidate compound and its ligand, assaying for inhibiting PSGR mediated signalling induced by said ligand which involves administering to a cell which expresses the PSGR polypeptide an effective amount of a PSGR agonist capable of decreasing PSGR mediated signalling.
In a further aspect, the present invention is directed to a method for enhancing PSGR mediated signalling induced by its ligand which involves administering to a cell which expresses the PSGR polypeptide an effective amount of a PSGR agonist or antagonist capable of increasing PSGR mediated signalling.
Whether any candidate xe2x80x9cagonistxe2x80x9d or xe2x80x9cantagonistxe2x80x9d of the present invention can enhance or inhibit PSGR mediated signalling can be determined using art-known G-protein coupled ligand/receptor cellular response assays, including those well known in the art. Thus, in a further aspect, a screening method is provided for determining whether a candidate agonist or antagonist is capable of enhancing or inhibiting a PSGR mediated cellular response to a ligand. The method involves contacting cellular response, and comparing the cellular response to a standard cellular response, the standard being assayed when contact is made with the ligand in absence of the candidate compound, whereby an increased cellular response over the standard indicates that the candidate compound is an agonist of the ligand/receptor signaling pathway and a decreased cellular response compared to the standard indicates that the candidate compound is an antagonist of the ligand/receptor signaling pathway. By the invention, a cell expressing the PSGR polypeptide can be contacted with either an endogenous or exogenously administered ligand.